The present invention relates to the field of mosaicing images. More specifically, the present invention relates to mosaicing, images of the eye to create high resolution, wide-field ophthalmic images for the diagnosis and treatment of eye diseases.
Diagnosis and treatment of ophthalmic disease in general, and retinal and optic nerve diseases in particular, rely heavily on photographic and angiographic imaging of the eye. These images are vital for clinical care in preventing and treating the most common causes of vision loss, including diabetic retinopathy and age-related macular degeneration. Photographic and angiographic images facilitate discovery of ophthalmic abnormalities by documenting changes to the eye over time. For example, abnormalities may be discovered in real-time by comparing images taken during a patient examination with previously taken photographic images.
To date, photographic images of the fundus (back of the eye or retina) are acquired with a standard fundus camera, available commercially from Carl Zeiss, Inc., model number FF450. The fundus camera provides a high quality, wide-field of view image of the fundus. However, because of its high cost and the fact that it is a dedicated instrument, offering no use other than photography, many optometrists and ophthalmologists opt not to have a fundus camera in their office. Therefore, fundus photography, is rarely performed during the routine examination that a majority of patients undergo. As a result, fundus photography is underutilized.
A direct ophthalmoscope and slitlamp biomicroscope, on the other hand, are instruments that are common to every examination room in an ophthalmologist""s and optometrist""s office. Furthermore, these instruments may be are attached to an image acquisition device, like a charge coupled device (CCD) camera. The CCD camera in combination with the direct opthalmoscope and slitlamp can acquire images of the back of the eye for documentation and communication purposes. However, because the direct ophthalmoscope and biomicroscope provide a reduced image quality and a far narrower field of view (as compared to the fundus camera), the images they provide are not useful for photodocumentation.
Presently, image processing techniques exist that construct mosaic representations from individual still and video imagery. These techniques include image registration, topology inference with local-to-global alignment (TILGA), and multiresolution blending, well known to those skilled in the art. Generally, partially overlapping individual images are combined and manipulated (using these processes) to provide a seamless mosaic effect. In particular, image registration refers to the alignment of the individual images. Topology inference is a process that automatically determines which image pairs are indeed overlapping, and local-to-global alignment simultaneously adjusts the placement of each image to be maximally consistent with all the pair-wise alignments. Multiresolution blending smoothly transitions the color and brightness between adjacent images, which otherwise may be radiometrically mismatched due to nonuniform illumination and sensor sensitivity. The mosaic""s overall resolution can be improved by signal estimation from overlapping images. In addition, image fusion may be used to enhance focus and dynamic range of the mosaic by combining the most salient features of each image at multiple resolutions.
Although these processing techniques have been successful in producing wide field of view mosaics in various applications (e.g., indoor, outdoor, and microscopic applications), they have failed when applied to direct ophthalmoscope and slitlamp imagery. This failure is due, in part, to the many unique characteristics of such imagery such as: narrow field of view, rapid movement of the subject eye, specular reflections, areas of low feature contrast, and geometric image distortion. Therefore, it would be useful to provide a system and method for mosaicing direct ophthalmoscope and slitlamp images.
In view of the above-mentioned limitations in the prior art, the present invention describes techniques for converting the direct ophthalmoscope""s and slitlamp biomicroscope""s low-quality, narrow field of view images into clinically useful high-quality, wide field of view images.
The invention is a method and system for mosaicing images of the eye to create high resolution, wide-field ophthalmic images for the diagnosis and treatment of eye diseases. The inventive method comprises acquiring a first image of the eye, acquiring a second image of the eye, and processing the images to produce a mosaic representation. The second image includes a portion of the first image. To guide in acquiring the second image, the method may include the step of viewing the first image while acquiring the second image. The method also may include the step of providing a direct ophthalmoscope or a slitlamp biomicroscope to acquire the images. The method further may comprise converting the images to a digital format. The step of processing includes aligning and merging the images, and conducting real-time processing and non-real-time processing. Real-time processing may include eliminating non-overlapping images, image registration, topology inference, local-to-global alignment, image fusion, signal estimation, and multiresolution blending. Non-real-time processing may include local alignment, global alignment, image registration, intra-alignment, inter-alignment, signal averaging, and photometric blending.
The inventive system for mosaicing images of the eye comprises an image acquisition device adapted to provide images of the eye, a camera coupled to the image acquisition device, a data processor coupled to the camera, a data storage device couple to the data processor, and a monitor coupled to the data processor. The image acquisition device may be a direct opthalmoscope or a slitlamp biomicroscope. The system also may include a selection unit coupled to the data processor, wherein the selection unit may be a keyboard, a mouse, or a microphone. The system further may include a converter coupled to the image acquisition device and the data storage device. The data processor may conduct both real-time and non-real-time processing. The real-time processing may include eliminating non-overlapping images, image registration, topology inference, local-to-global alignment, image fusion, signal estimation, and multiresolution blending. The non-real-time processing may include image registration, topology inference, local-to-global alignment, image fusion, signal estimation, and/or multiresolution blending.
The invention further includes a method of detecting eye diseases. The inventive method comprises examining the eye using an image acquisition device, capturing images of the eye, wherein each of the images includes a portion of another image, aligning and merging the images to create a mosaic representation, viewing the mosaic representations, and detecting eye diseases. The step of examining may be conducted using a direct ophthalmoscope or a slitlamp biomicroscope.
The invention also includes a method of creating a mosaic representation of the eye. The method comprises providing an image acquisition device adapted to acquire images of the eye. The image acquisition device may include, for example, a direct ophthalmoscope or a slitlamp biomicroscope. The image acquisition device allows a user to select a first image of a first portion of the eye. The user then moves the image acquisition device to a second portion of the eye, wherein the second portion overlaps the first portion. A second image of the second portion of the eye is then acquired. As the image acquisition device is moved, the first image may be viewed to assist in ensuring overlap with the second image. Acquiring the second image may include automatically capturing images from a stream of images provide by the image acquisition device. The images are processed to create a mosaic representation of the eye. The processing may include merging and aligning the images.